net: add SetKeepAlivePeriod

Sets both the duration from the last data packet to the first
keep alive packet and the duration between keep alive packets to be
the passed duration.

I've tested the function on both Darwin (10.8.4) and 4.2 Linux.
I've compiled (make.bash) for all the OS's and tested (all.bash)
on Darwin and Linux.

R=golang-dev, dave, rsc, dvyukov, presotto+facebook, nick
CC=golang-dev, veyron-team
https://golang.org/cl/11130044

src/pkg/net/tcpsock_posix.go

@@ -121,6 +121,14 @@ func (c *TCPConn) SetKeepAlive(keepalive bool) error {
 	return setKeepAlive(c.fd, keepalive)
 }
 
+// SetKeepAliveIdlePeriod sets period between keep alives.
+func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return setKeepAlivePeriod(c.fd, d)
+}
+
 // SetNoDelay controls whether the operating system should delay
 // packet transmission in hopes of sending fewer packets (Nagle's
 // algorithm).  The default is true (no delay), meaning that data is

src/pkg/net/tcpsockopt_darwin.go

+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TCP socket options for darwin
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// Set keep alive period.
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	if err := fd.incref(false); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	// The kernel expects seconds so round to next highest second.
+	d += (time.Second - time.Nanosecond)
+	secs := int(d.Seconds())
+
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPALIVE, secs))
+}

src/pkg/net/tcpsockopt_openbsd.go

+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TCP socket options for openbsd
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// Set keep alive period.
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	if err := fd.incref(false); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	// The kernel expects seconds so round to next highest second.
+	d += (time.Second - time.Nanosecond)
+	secs := int(d.Seconds())
+
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPALIVE, secs))
+}

src/pkg/net/tcpsockopt_posix.go

+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build freebsd linux netbsd
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// Set keep alive period.
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	if err := fd.incref(false); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	// The kernel expects seconds so round to next highest second.
+	d += (time.Second - time.Nanosecond)
+	secs := int(d.Seconds())
+
+	err := os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPINTVL, secs))
+	if err != nil {
+		return err
+	}
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPIDLE, secs))
+}

src/pkg/net/tcpsockopt_windows.go

+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TCP socket options for windows
+
+package net
+
+import (
+	"time"
+)
+
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	if err := fd.incref(false); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	// We can't actually set this per connection.  Act as a noop rather than an error.
+	return nil
+}